Magnification difference from resolution

There are several types of acoustic microscopes, which differ from one another mainly in the principle of transforming the acoustic image into a visible one. The lens scanning acoustic microscope is widely used [107]. The specification of a modem acoustic microscope is as follows frequency range 50-3000 MHz, resolution 50-0.1 ira, magnification 50-5000, and depth of penetration 1 p to 1 mm. 

Optical interferometry can be used to measure surface features without contact. Light reflected from the surface of interest interferes with light from an optically flat reference surface. Deviations in the fnnge pattern produced by the interference are related to differences in surface height. The interferometer can be moved to quantify the deviations. Lateral resolution is determined by the resolution of the magnification optics. If an imaging array is used, three-dimensional (3D) information can be provided. 

The primary difference between optical and electron microscopy is that the latter uses an electron beam as the probe. Since 10- to 500-keV electron beams have much lower wavelengths than light, the resolution is greater. At the same time, the electron beam requires completely different instrumentation (source, collimator, detector, magnification control, etc.). Moreover, electrons are very readily absorbed by matter. Therefore, the entire path of the beam, from source to specimen to detector, has to be in vacuum. From the sample preparation point of view, this is of major significance. For specimens that may change in vacuum, biological tissues, for instance, this can be a major concern, and newly developed accessories such as environmental cells [8] need to be added to the microscope. 

Advances in light microscopy have allowed the magnification of objects up to 1,000 times their original size and improved the resolution of the human eye from 0.1 mm to 0.2 Xm (see Table 1 for a comparison of the different visualization techniques). With the aid of histochemical, fluorescence, and autoradiographic methods, in particular, the use of light microscopy in the biological sciences has revealed the substructure of tissues and dynamic processes within cells. 

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